Well gravelling tool

ABSTRACT

Apparatus for dispersing and packing gravel within the annulus of a tubular member positioned within a well comprising the combination of a drill pipe string and a well gravelling tool operatively communicated therewith. The well gravelling tool per se comprises a pair of concentric members, a smaller diameter member mounted within a larger diameter tubular member, the difference between the diameters being sufficient to provide an annular opening which is communicated to the opening through the drill pipe string. The drill pipe string and well gravelling tool are operatively engageable e.g., via threadable connections, one member with the other, and the well gravelling tool in turn is engageable, e.g., via threadable connection, of opposite cast, with a tubular member located within the bottom of the well to seal the interior of the latter from entry of fluid or gravel. Gravel can be discharged downwardly from the surface through the drill pipe string and well gravelling tool to fill the annulus of the well inside the casing, and outside the tubular element. Fluid can then be forced down into the well via the drill pipe string and well gravelling tool, under pressure, to pack the gravel. Upon release of the pressure, additional gravel can be added and, after setting, any excess gravel can be returned to the surface with reverse circulated fluid which descends down the annulus between the casing and drill pipe string, and ascends through the well gravelling tool and drill pipe string.

l g SHELL-SIDE LIQUID METAL BOILER ORIGIN OF INVENTION BACKGROUND or THE INVENTION 1. Field of the Invention The field of the invention relates to liquid metal boilers and more particularly to boilers employed in heating liquid metals for use in generating electrical power within Rankine cyclev systems.

2. Description of the Prior Art Energy conversion systems are notoriously old. However, where electrical energy is obtained-through a thermal energy conversion system it has been found that about 50 percent to 80 percent of the available heat must be radiated or rejected. Liquid metal radiators provide radiation and rejection of energy at high temperatures of operation. Liquid metal boilers are deemed to be particularly useful in Rankine cycle systems'and are suited for use with nuclear reactors. Howeverfliquid metal boilers heretofore available have not totally satisfied existing needs.

The prior art includes liquid metal boilers wherein a'plurality of parallel tubes serve as conduits for conducting liquid metals alongparallel paths through a heat transfer zone of a heat exchanger so that heat is transferred to the liquidmetal as the metal flows through-the tubes for thereby-converting the liquid metal to its vapor state. Such boilers inherently lack the capability of providing a 100 percent pure vapor, free fro surged and'splashed liquid'and liquid spray.

In employing metal boilers of the prior art'variety, wherein the metal is heated as it-is-delivered through parallel'tubes for conduits, total vaporization of metals is quite difficult to achieve, as such requires that the liquid remain in contact with the walls of the heated conduits. This, of course,requires the liquid to be delivered in streams of a tubular configuration having a vapor core. As a practical matter such delivery cannot be achieved. Furthermore, where the metal is confined as a mixture of vapor and liquid slugging" invariably occurs, since the vapor tends to force slugs" of liquid through the conduits.

Another dilficulty often encountered in employing parallel conduits for delivering liquid metals through a heat transfer zone of a heat exchanger is system instability which-arisesas a result of the fact that different" rates of vaporization-simultaneously occurs withintheseveral conduits.

Therefore, even though nuclear reactors constitute ideal sources of energy for Rankine cycle systems there exists a need for'a practical boiler to boil liquid metals 'with a high degree of efficiencyand predictability. This isparticularly true wheresuch systems are employed aboard-space craft for use in space flight operations of an extended'duration.

OBJECTS AND SUMMARY OF THE INVENTION It is therefore an object of the instant invention toprovide animproved liquid metal boiler which employs a tubeand shell heat exchanger having a high degree of operational stability.

Another object is toprovide an improved metalboiler particularly suited for use in imposing a change of phase on liquid alkali metals for achieving metal vapors through shell-side boiling.

Another object is to provide an improved liquid metal boiler which is adapted to impose a change of phase on alkali metals with a high degree of predictability.

Another object is to provide an improved liquid metal boiler which isadapted to achieve'shell-side boiling of potassium.

Another object is to provide an improved liquid metal boiler for converting .cooledliquid potassium to a heated vapor by achieving a heat exchange between liquid lithium and the potassium as the potassium is caused to circulate about tubular conduits employed in delivering heated lithium through the boiler.

Another object is to provide an improved shell-side liquid metal boiler adapted to conduct a heated primary fluid through a plurality of spaced, tubular conduits, and to deliver a secondary fluid along a tortuous path having both crossflow andspiral-flow path components extending about the conduits so that a change of phase is imposed on the secondary fluid as it progresses through the boiler.

Another objectis to provide unimproved liquid metal boiler .for converting liquid alkali metal to heated vapor byachieving a heatexchange between liquid metals through conduction, as the alkali metal is'caused to circulate about tubular conduits employed in delivering a heated fluid therethrough, whereby a heat exchange through conduction is achieved.

Another object is to provide within a liquid metal shell-side boiler a plurality of substantially parallel baffle plates for directing liquid potassiumalong a tortuous path having both crossflow and spiral-flow .path components circumscribing a heat delivery system including a bundle of substantially parallel, spaced tubular conduits through-which heated liquid lithium is delivered :in order that the lithium be permitted to give up relativelylarge quantities of heat to the potassium for achieving a heat exchange therebetween, whereby the potassium is caused to undergoachange of phase from a'liquid to a vapor having a high exit quality extending into vapor superheat.

These and other objects .and advantages of the instant invention are achieved by providing a liquid metal boiler having a shell of a tubular configuration circumscribing a plurality of axially extended, lithium conducting conduits and baffle platesarranged within the shell in a manner such that circulation of liquidpotassium about the conduits is achieved to effect shell-side boiling of the potassium as it is caused to progress along a tortuous path, having both spiral and crossflow path components extending between'the adjacent surfaces of the conduits'and the boiler shell.

BRIEF DESCRIPTION OF 'THEDRAWINGS FIG. I'is a diagrammatic view of the system embodying the shell-side liquid metal boiler of the instant invention.

FIG. 2 is a flow diagramdepicting the path of flow for'primary and secondary fluids as the fluids are caused to flow along adjacent paths through the boilerillustrated inFIG. 1.

FIG. 3 is a cross-sectional elevation of the boiler shown in FIG. 1, illustrating the relationshipestablished between the conduits utilized in conducting a primary fluid through the boiler and the battle plates employed in delivering a secondary fluid along a tortuous path having both .crossflow and spiralflow path components and extending about the conduits.

FIG. 4 is a cross-sectional view taken generally along line 4-4 of FIG. '3.

FIG. 5 is a cross-sectional elevationof a modified form of the boiler shown-in FIG. I.

DESCRIPTION'OF THE PREFERRED EMBODIMENT Turning to FIG. I, therein is illustrated a shell-side liquid metal boiler 10 operativel'y disposed within Rankine cycle power system. As shown, the system includes a primary loop 12 and a secondary loop 14. Theprimary loop is adapted to deliver heated liquid lithium tothe boiler 10 for purposes of achieving a transfer of heat while the secondary loop 14 is such systems, a detailed description thereof is omitted in the interest of brevity. However, it is to be understood that the pri- PATENTED Bites ml 3 30 27 7 FIG. 4.

FIG. 3.

FIG. 2.

FIG. I.

I N INVENTOR.

DALLAS C. SMITH BY ionam ATTORNEY WELL GRAVELLING TOOL It is conventional in drilling deep wells to position tubularshaped members, including foraminous liners or sand screens, within well cavities at locations of producing sand stratums, within well bores. In a typical arrangement, e.g., tubularshaped members, or blank pipes, are alternately placed with the sand screens, one atop the other. Gravel is placed about such members to prevent caving, spillage, and influx of sand via the screens into the well. Several types of apparatus, or gravel pack systems, are known to the art.

The gravel-packing apparatus, or systems, employed is so structured to provide means for depositing gravel about the outer face of the tubular elements, e.g., the screen or foraminous liner, while precluding deposition of gravel inside the liner. In some systems, such as the hydraulic packing system described by U.S. Pat. No. 2,372,46l, granted to L. C. Uren, the lower portion of the well bore is capped off, the top of the liner is temporarily plugged, and a gravel slurry is pumped downwardly from the surface through a string of tubing, which encloses the liner. The slurry is passed downwardly, through the annular opening between the tubing and the liner, and out the lower terminal end of the tubing. The gravel settles within the cavity or annular space between the well wall and the liner, and liquid ascends through the annulus between the well wall and the said tubing to the surface.

Other types of systems comprise apparatus wherein gravel is contained within bailers, or containers, let down upon wire or cable from the surface to the well bottom. For example, apparatus of such type is described in U.S. Pat. No. 2,140,072, granted to R. L. Chenault. A cable-conveyed container, for retention of the gravel, is provided with valve means adjacent the bottom of the container. The valve is constructed so that the gravel-filled container is normally closed to retain the gravel, but is adapted to open on contact of the bottom of the container with the liner about which gravel is to be packed. Another apparatus of such general character is described by U.S. Pat. No. 3,182,723, granted to W. K. Layne, Sr. This device is also characterized as a cable-conveyed bailer beneath which is suspended a smaller diameter double-end conical-shaped baffle device, a lower end of which is to contact and block off the liner to the flow of solids while the upper end is employed to better distribute the gravel upon its release from the bailer. The bailer is provided with a frangible disk upon which the gravel rests, and adjacent thereto is provided a remotely controlled explosive cap. The explosive cap is set off from the surface to rupture the fragile disk and release gravel from the bailer. While these and other such devices have proven useful for the purpose intended, all are too complex. One major difficulty, particularly with the bailer-type devices, is that considerable time is required for the many trips down the well bore. The necessity of the many incremental releases of gravel and the great number of repetitive steps involved in gravel packing is unduly burdensome. Moreover, it is necessary to make very accurate and exact calculations in discharging gravel into a well for there is no way to return excess gravel resulting from overfills. Less complex devices, capable of more rapid operation, but yet capable of a high degree of precision by ordinary operating labor, are needed.

It is accordingly the primary objective of the present invention to fulfill these and other needs, as well as to obviate the foregoing and other problems.

An object of the present invention, specifically, is to provide a new and novel apparatus for depositing gravel and like materials into annuli about tubular elements positioned in well bores or casings.

A more specific object is to provide apparatus of such character which does not require repetitive trips down the well, or the introduction of exact amounts of gravel, but rather inexact amounts, permitting ready removal of excess amounts of gravel.

These and other objects are achieved in accordance with this invention which comprises the combination of a drill pipe string and a well gravelling tool. The latter is operatively engaged with the drill pipe string, by virtue of which gravel can be discharged or passed downwardly from the surface through the drill pipe string, through an annular opening within the well gravelling tool itself, and then discharged and packed about the annulus of a tubular member, or foraminous liner, located within the well. Excess gravel, if any, can then be returned to the surface by passage of fluid downwardly between the annular opening formed between the outside of the drill pipe string and the well bore, so that excess gravel is picked up by the fluid and returned upwardly through the annulus within the well gravelling tool and opening through the drill pipe string.

The well gravelling tool per se is comprised of a pair of concentric members, an outer larger diameter hollow tubular member and, mounted therein, an inner cylindrical member of sufficiently smaller external diameter to provide an annular opening through the said outer member. The inner cylindrical member is enclosed or blocked at the top, preferably by a conical-shaped member which forms an apex upon which downwardly falling gravel is radially outwardly directed into the annular opening formed between the two members. The lower portion of the inner tubular member is provided with means for operative engagement with the tubular member positioned within the well, for sealing it off to the flow of gravel and fluid.

These and other features and advantages will be better understood by reference to the following detailed description and to the accompanying drawings to which reference is made in the description.

Referring to the drawings:

FIG. 1 is a partial section elevation view showing the combination of a segment of a drill pipe string and a preferred type of well gravelling tool.

FIG. 2 is a plan view, taken along section 2-2 of the preceding figure, showing structural details of the well gravelling tool.

FIG. 3 is an elevation view illustrating the initial step of lowering the drill pipe string and well gravelling tool into a well, the interrelationship thereof with the tubular member being placed at the bottom of the well, and the technique of dispersing and packing gravel around the tubular member.

HO. 4 is a sectional elevation view similar to the preceding figure showing the technique by which excess gravel is removed from the well.

Referring to FIG. 1,, there is shown a preferred gravelpacking apparatus or well gravelling tool 10 in combination with a string of drill pipe 9, in net effect, a hollow tubular shell extendable from the surface downwardly into the well to which the former is operatively connected and communicated during a well-packing operation. The well gravelling tool 10 is constituted of a pair of concentric members, an outer tubular member 11 and an inner cylindrical or tubular member 12. The difference between the internal diameter of the outer tubular member 11 and the external diameter of the inner tubular member 12 is such as to provide an annular passageway 13. The central or inner member 12 is held in place within tubular member ll by any convenient means which does not unduly block the passageway 13, e.g., a webbing as formed by spacers 14,, 14,, 14 and M secured in place by welding points, located apart around the circumference of the said members. These details are also shown by specific reference to the second figure.

The upper wall portion of the outer tubular member 11 is tapered inwardly forming a nozzle portion 15 which is externally threaded and joined via an internally threaded collar to the externally threaded drill pipe 9. The upper portion of the inner member 12 is conical shaped, and the lower portion thereof is threaded for connection with, and the sealing of, a tubular element such as is located at the bottom of the well to be packed.

The cast of the external threads on nozzle 15 and the terminal end of drill pipe 9 are similar so that these members can be conveniently tightened into the collar 16 by turning a member in a given direction. On the other hand, the cast of the external threads on the lower end of inner member 12 is just the opposite. This is so that the drill pipe string 9 and the well gravelling tool 10 can be made up and secured to a tubular element which is to be lowered into a well bore, but yet the well gravelling tool 10 can be easily uncoupled therefrom by rotation of the drill pipe string 9 without uncoupling of the well gravelling tool 10. Preferably, the external threads of nozzle l5 and the pipe 9 are right-hand threads, and the threads located on the lower end of inner member 12 are left-hand threads.

ln FIGS. 3 and 4 there is shown a well or borehole, provided with a casing 19, drilled into a producing formation which comprises a producing zone A and a nonproducing zone B. A tubular screen 21 is provided within producing zone A so that oil can flow therethrough into the screen interior. An additional tubular screen 22 is to be provided within the producing zone A, prior to the addition of ordinary production tubing as in, e.g., zone B.

in initiating an operation, at a location outside the well, the drill pipe string 9, well gravelling tool 10 and screen 22 are secured together. The terminal end of the segment of drill pipe 9 is thus coupled to the well gravelling tool 10 via threadable engagement to the collar 16. Right-handed threads are employed to couple together these members. The well gravelling tool 10, in turn, is coupled to the screen 22 via threadable engagement between the lower portion of member 12 and the collar 23. Left-handed threads are employed to couple these members. The coupled members 9, 10, 22 are then lowered into the well, as shown by reference to FIG. 3, until the lower end of the pipe blank 22 engages the collar 24 coupled via lefthanded threads to screen 21. Rotation of the assembly to the left secures the pipe blank 22 to the screen 21 via threadable engagement to the collar 24.

An amount of gravel believed to approximate that required to pack the annulus between the tubular members 21, 22 and the casing 19 above the shoe 25 is poured downwardly through the opening within drill pipe string 9. The falling gravel is deflected radially outwardly and into the annulus 13 of well gravelling tool 10, filling the annulus between the tubular members 21, 22 and casing 19 to an even level to the top of zone A.

Fluid is then passed downwardly through the drill pipe string 9, the annulus of well gravelling tool 10, and from about 800-1 ,000 p.s.i.g. pressure is applied on the gravel pack. This assures a solid pack and prevents any tendency of bridging. The pressure is then released.

It is preferable to add additional gravel at this point to provide an even solid pack. After release of the fluid pressure, additional gravel is thus added and permitted to set, e.g., for about 2 hours. Fluid is then pumped down the annulus, between the drill pipe string 9 and the casing 19, causing a reverse circulation of fluid as shown by reference to FIG. 4. The reverse circulation of fluid picks up any excess gravel and carries it up through the annulus of the well gravelling tool 10 and drill pipe string 9 and out of the well.

After completion of the reverse circulation, the drill pipe string is rotated to the right to disengage the well gravelling tool 10 from the screen 22. The tool 10 is then lifted or retrieved from the well. The process is thus completed and ready for production tubing to be run to complete the well.

It is apparent that various modifications and changes, such as in absolute or relative dimensions of theparts, materials used and the like, can be made without departing the spirit and scope of the invention as will be apparent to those skilled in the art.

Having described the invention, what is claimed is:

1. Apparatus for dispersing and packing gravel within the annulus of a tubular member which is lowered into and positioned upon another tubular member located in a well, comprising, in combination,

a drill pipe string, in net effect, a hollow tubular shell which can be freely lowered from the surface downwardly into the well, and then raised,

a well gravelling tool continuously operatively engaged to the terminal end of the drill pipe string while packing gravel comprising a pair of concentric members including a large diameter hollow tubular member with means located at the top portion thereof for engagement with the lower portion of the hollow tubular shell of the drill pipe string to which it is communicated, and a top permanently enclosed cylindrical-shaped member, mounted within the large tubular member, of sufficiently smaller diameter to provide an annular opening leading downwardly from the top portion of the outer tubular member to its lower extremity, which provides an outlet, said cylindrical shaped member being attached to the inside of the said outer tubular member via connecting webbing which does not unduly restrict the passageway between the said members, and the lower extremity of the said cylindrical member is threaded and adapted for threadable engagement with the said tubular member for lowering, positioning and sealing the tubular member upon another said tubular member located in the well, whereby gravel can be passed downwardly from the surface through the hollow tubular shell constituting the drill pipe string, through the annulus between the pair of concentric members constituting the well gravelling tool, dispersed about the annulus of the tubular member positioned in the well, and then packed by application of pressurized fluid upon the gravel and, completion of the gravel dispersement and packing can be indicated by reverse circulation and passage of fluid downwardly into the well on the outside of the drill pipe string, which fluid is returned upwardly through the said annulus of the well gravelling tool and through the inside of the hollow tubular shell constituting the drill pipe string so that excess gravel is returned to the surface.

2. The apparatus of claim 1 wherein the cylindrical member is welded to the outer tubular member, four connecting webbings being employed, each about apart.

3. The apparatus of claim 1 wherein the lower extremity of the hollow tubular shell of the drill pipe string is threadably engageable with the upper portion of the outer tubular member, the lower extremity of the inner cylindrical member is threadably engageable with an end of the tubular member which is lowered into and positioned in the well, and the threads of the outer tubular member and inner cylindrical member are of opposite cast.

4. The apparatus of claim 3 wherein the upper portion of the outer tubular member is provided with a right-hand thread and the lower portion of the cylindrical member is provided with a left-hand thread. 

1. Apparatus for dispersing and packing gravel within the annulus of a tubular member which is lowered into and positioned upon another tubular member located in a well, comprising, in combination, a drill pipe string, in net effect, a hollow tubular shell which can be freely lowered from the surface downwardly into the well, and then raised, a well gravelling tool continuously operatively engaged to the terminal end of the drill pipe string while packing gravel comprising a pair of concentric members including a large diameter hollow tubular member with means located at the top portion thereof for engagement with the lower portion of the hollow tubular shell of the drill pipe string to which it is communicated, and a top permanently enclosed cylindrical-shaped member, mounted within the larger tubular member, of sufficiently smaller diameter to provide an annular opening leading downwardly from the top portion of the outer tubular member to its lower extremity, which provides an outlet, said cylindrical shaped member being attached to the inside of the said outer tubular member via connecting webbing which does not unduly restrict the passageway between the said members, and the lower extremity of the said cylindrical member is threaded and adapted for threadable engagement with the said tubular member for lowering, positioning and sealing the tubular member upon another said tubular member located in the well, whereby gravel can be passed downwardly from the surface through the hollow tubular shell constituting the drill pipe string, through the annulus between the pair of concentric members constituting the well gravelling tool, dispersed about the annulus of the tubulaR member positioned in the well, and then packed by application of pressurized fluid upon the gravel and, completion of the gravel dispersement and packing can be indicated by reverse circulation and passage of fluid downwardly into the well on the outside of the drill pipe string, which fluid is returned upwardly through the said annulus of the well gravelling tool and through the inside of the hollow tubular shell constituting the drill pipe string so that excess gravel is returned to the surface.
 2. The apparatus of claim 1 wherein the cylindrical member is welded to the outer tubular member, four connecting webbings being employed, each about 90* apart.
 3. The apparatus of claim 1 wherein the lower extremity of the hollow tubular shell of the drill pipe string is threadably engageable with the upper portion of the outer tubular member, the lower extremity of the inner cylindrical member is threadably engageable with an end of the tubular member which is lowered into and positioned in the well, and the threads of the outer tubular member and inner cylindrical member are of opposite cast.
 4. The apparatus of claim 3 wherein the upper portion of the outer tubular member is provided with a right-hand thread and the lower portion of the cylindrical member is provided with a left-hand thread. 